high power couplers for tesla sl cavities2

8/9/2019 High Power Couplers for TESLA SL Cavities2

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High Power Couplers for

TESLA SL CavitiesWolf-Dietrich Mller

DESY

1. TESLA Coupler Specification

2. Design Criteria3. TTF 3 Coupler

4. Couplers in use at TTF-FEL

5. Tests at 35 MV/m

6. Industrial Study of the TTF 3 Coupler for X-FEL

7. Other Developments

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1. Specification of the TESLA High Power

Coupler

TTFTESLA

9-cell / upgrade

TESLAsuperstructure /

upgrade

beam power incl.control margin

250 kW250 kW / 500kW

555 kW / 1110kW

repetition rate 10 Hz 5 Hz 5 Hz

couplingadjustable

( 106 - 107 )

fix

( 3*106 )

fix

( 2.5*106 )

cavity positionduring cool down

flexible(15 mmlongitudinal)

fix point(1.5 mmlongitudinal)

fix point(1.5 mmlongitudinal)

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General Parameters

frequency 1.3 GHz

operation

pulsed: 500 sec risetime,

800 sec flat top with beam

power for High Power

Processing in situ

1 MW at reduced pulse length

( 500 sec and repetition rate 1 Hz )

2 K heat load 0.06 W

4 K heat load 0.5 W

70 K heat load 6 W

diagnosticsufficient for safe operation and

monitoring

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2. Design criteria for the TESLA Coupler

coax is easy for: - variable coupling

- fabrication

- assemblytwo windows for: - clean assembly of the cavity

- save operation

cold coax: - at 70 Ohm, 40 mm diameter warm coax: - at 50 Ohm, 60 mm diameter

bias on inner conductor: - suppress multipacting

flexibility: - bellows in the warm and cold coaxceramics: - Al2O3 with TiN coating

copper plating: - 10/30 m outer/inner coax

- high thermal conductivity (RRR 30)- high purity, Hydrogen free 4


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Multipacting as a Design Criteria

in order to avoid multipacting during conditioning andoperating one has to:

- choose the right coaxial line diameter (MP level moves upwith the 4thpower)

- the right impedance (MP level moves up linear)- lower the secondary electron emission coefficient on the

surfaces (especially the ceramic)

- add a bias voltage to the inner conductor to suppressmultipacting

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3. TESLA Coupler TTF 3

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FNAL TTF II TTF IIIwindow conical cyl. cyl.

coax diameter, m 40 40 40

Impedance, Ohm 50 70 70

window flat, WG flat, WG cyl.

coax diameter, m 60 60 60

Impedance, Ohm 50 50 50

adjustable adjustable adjustable

no yes yes

FermiLab FermiLab DESY

2Hz / 500s 1MW 2MW 1MW2Hz / 1.3ms 1MW 1.8MW 1MW

cold test done yes no no

2Hz /


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5. Tests at 35 MV/m

Long run test of EP cavities in the horizontal cryostat

o This test includes all auxiliaries like power coupler, HOM

coupler, tuner, piezoo Gradient: 35 MV/m

o Max forward power: 600 kW

o RF on time 2400 hso No breakdowns in the coupler

High gradient test with beam (in module ACC1)

o Gradient: 35 MV/m

o Gradient calibration with beam8


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6. Industrial Study

of the TTF 3 Coupler for X-FEL

(Collaboration between LAL & DESY)

Publication of the call for candidacy was on February 15th 2005,

study will finish February 2007 with delivery of two prototypes.Three companies will be involved.

Goals:

minimize risks related to project:

all technical issues will be solved

development plan ready

minimize financial risks: precise estimation of cost in series

assurance that the chosen contractors will succeed

gain time on manufacturing contract: all studies are done9

S. Prat, LAL


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Principle ofDefinition contract for industrialisation studies

Essentially intellectual work:

Define all manufacturing processes

Risk analysis (process, logistics) Determine cost in series and justify

Produce validation models and 2 prototypes

Particularities

3 contracts will be awarded on the same subject

these contracts will run simultaneously during 21 months evaluation of performance will be continuous ( formal reviews are key points)

2 teams will be selected after final evaluation

contracts for manufacturing 2 series of 500 XFEL couplers will be awarded

without new call for tenders

the 2 contracts may be awarded to a single company S. Prat, LAL


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Status of additional work

Study of geometrical tolerances (RF studies) Thermal studies (analytical + FEA)

RF studies of capacitor

Control electronics

Conditionning studies

EDMS

TiN coating technology

Interfaces definition with:

WP3, WP8, WP9, WP19, WP28, WP29, WP33,WP34, WP36

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Completed

In progress

Not started

S. Prat, LAL


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Time schedule (now shifted by 2 month)

12S. Prat, LAL


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TTF 4 coupler

80 mm coax

Foreseen for the 4 x 7 cell superstructure

Two prototypes build & tested at LAL

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LAL Design

Coax 60 mm

Disc windows Under construction

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AMAC - DESY Collaboration

80 mm coax Two prototypes fabricated and under test

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Conclusion

62 TTF 3 couplers are fabricated

24 are tested 11 TTF 3 couplers are under operation in TTF

Several tests at Eacc 35 MV/m done

One test at 35 MV/m over 2400 hrs

No breakdowns in the coupler

Industrial study for the X-FEL is started

Coupler developments for higher power (bigger coax

diameter) is under way

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high power couplers for tesla sl cavities2

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